ISTS Symposium43 Program/Agenda

Sea turtles are transboundary—their movements and migrations connect distant habitats, thereby linking diverse research projects, communities, and management entities. Therefore, sea turtle conservation is also transboundary, and human cooperation at the scale of regions, RMUs, and beyond can significantly improve our ability to support population recovery. Here, we introduce a multinational collaboration within the Western Atlantic, pooling data among research programs across the region to present a large-scale panorama of hawksbill sea turtle (Eretmochelys imbricata) movement and habitat use. We synthesize satellite telemetry data for over 250 adult females, identifying key migratory corridors, high-use foraging areas, and geographic data gaps. We also use the regional dataset to evaluate patterns in hawksbill migratory distance and bathymetry use. Broadly, our findings indicate high rates of basin-wide migratory connectivity, yet also show a diversity of migratory strategies, including many turtles that remain within the exclusive economic zone of their nesting site. Satellite tracks reveal that hawksbills establish residency in neritic foraging habitats throughout the region, including multiple high-use areas that may be worthy of elevated management focus, such as the Nicaragua Rise. Our findings represent just the first step in a project that we envision will evolve as more turtles are tracked and secondary analyses are conducted (e.g., spatial overlap with threats). We demonstrate how reanalysis and synthesis of existing data can advance our capacity to conserve sea turtle populations.

Hawksbill sea turtles (Eretmochelys imbricata) rely on coastal habitats for foraging and refuge, yet little is known about how human activity influences their localized distribution. Limited studies suggest that boat traffic and snorkeling can alter hawksbill behavior, affecting foraging and surfacing time, while others find no clear relationship between human presence and abundance. To explore this gap, we conducted in-water surveys in St. John, USVI, and Carriacou, Grenada, over two field seasons (2023–2024). Sampling occurred over 21 days in St. John and 22 in Carriacou, with four free divers working from boats to hand-capture turtles. Sites were categorized as “high” or “low” human-use based on local knowledge, accounting for boat traffic, snorkeling, and scuba diving. Daily Catch Per Unit Effort (CPUE) was calculated for each site, and non-parametric tests compared CPUE between human-use levels. Across both locations, turtles were significantly less prevalent in high-use areas. In St. John, mean CPUE was 0.002139 in low-use sites and 0.000704 in high-use sites (Mann-Whitney U = 21.5, p = 0.011). In Carriacou, mean CPUE was 0.0048 in low-use sites and 0.0001 in high-use sites (Mann-Whitney U = 10.00, p = 0.000734). No significant differences in benthic habitat composition were observed between human-use levels. This suggests hawksbill avoidance of high-use areas is behavioral rather than habitat-driven, indicating habitat protection alone may not be sufficient for conservation. However, we did not measure other environmental factors that may influence distribution. Further research is needed to clarify hawksbill-specific responses to human marine activity and disentangle the relative influence of environmental and anthropogenic drivers.

Hawksbill turtles (Eretmochelys imbricata) are a migratory species found globally in tropical regions. Vanuatu has several known hawksbill nesting sites on multiple islands including Moso Island (Hickey et al., 2023). Previous work with seven satellite tagged postnesting hawksbills (Jim et al, 2022) has shown that those nesting on Moso Island have come from home ranges on the Great Barrier Reef (GBR)(3), New Caledonia (3) and Aneityum Island, Vanuatu (1). This study expands on these findings, examining the post-nesting migration and home ranges of four additional turtles tagged with satellite transmitters in 2023 and 2024 with an added focus on migratory speeds at neritic and oceanic locations along with sea surface temperatures and chlorophyll concentrations along the turtlesʻ migratory routes.

Satellite tags were deployed on four post-nesting female hawksbill turtles on Moso Island in January 2023 (Makala) and January 2024 (Vatu Mau, Bule Lapa and Vonu e Rao). Makala traveled to Olympic Reef in the GBR, Vonu e Rao migrated to Emperor Reef in the GBR, Vatu Mau traveled to southern New Caledonia, Réserve Intégrale Yves Merlet, and Bule Lapa migrated to Australia’s Donovan Shoal.

Makala traveled 67 days from nesting ground to home range area in GBR, traveling 1842 km, at an average speed of 1.45 km/hr. Vonu e Rao reached her home range in GBR, traveling 2575 km in 57 days at 1.85 km/hr. Bule Lapa traveled 2695 km to her home range in 82 days at 1.36 km/hr, and Vatu Mau traveled 692 km to southern New Caledonia in 26 days at 1.10 km/hr. All four turtles slowed in neritic area (200m) versus oceanic segments (deeper than 200m), averaging 0.85 km/hr in their neritic segments, and 2.03 km/hr in oceanic segments.

Home range kernel densities were analyzed at 95% and 50% levels using Zoatrack software. Makala had a 95% kernel density of 0.6 km² and a 50% density of 0.1 km². Vonu e Rao’s home range was 8.8 km² (95%) and 1.3 km² (50%), Vatu Mau’s were 1.6 km² (95%) and 0.2 km² (50%), and Bule Lapa’s were 5.4 km² (95%) and 0.6 km² (50%) of home range.

This study confirms the connection between hawksbill turtles nesting on Moso Island and home ranges in New Caledonia and Australia, and expands upon the importance of neritic areas along migratory routes. Varying travel speeds during neritic and oceanic stages of migration from nesting to home ranges suggest resting or feeding in shallow areas. Home range habitat area varied with 95% KUD ranging from 0.624 km² to 8.8 km² for the four tagged turtles.

A growing number of studies have revealed that marine turtles exhibit complex and frequent social behaviors at various life-stages; however, the ecological and evolutionary purposes of these interactions are still relatively unknown. Using underwater camera surveys in Brewers Bay, St. Thomas, U.S. Virgin Islands, we conducted 89 hours of snorkel surveys with handheld cameras from October 2023 to September 2024 to document over 300 examples of social behaviors in green turtles. All interactions were categorized using an ethogram including the following behaviors: approach, bite, contact, displacement, group feeding, group resting, head touch, inspection, and pursuit. Interactions were further categorized as passive or aggressive. Aggressive behaviors entailed displays of dominance, like physical altercations, while passive behaviors were ultimately described as behaviors not encompassed in the aggressive definition. For each interaction, we recorded the local habitat (seagrass, rocky and coral, sand, and near anthropogenic structures), whether the instigating turtle was larger or smaller than the other, seasonality, time of day, and weather conditions. We compared models to assess the relationship between the extrinsic factors, the individual behaviors seen, and the aggressive or passive nature of the behavior. Overall, a majority of the interactions documented were passive and occurred in seagrass habitats. The behaviors most frequently observed were group feeding and approach, with biting being the least observed behavior. This study expands on the growing literature regarding marine turtle sociality by providing additional evidence of nuanced social interactions and by assessing the role habitat and other external variables can have on marine turtle interactions.

South Africa is home to two species of nesting sea turtles, the leatherback and loggerhead. Nesting occurs along the northeastern coastline during early summer. After hatching, neonates are swept southward by the warm Agulhas current. As the current retroflects, many young turtles are pushed into cold coastal waters, where they strand on beaches, sometimes injured and often exhibiting cold shock.

The Two Oceans Aquarium Foundation, through its Turtle Conservation Centre (TCC), has been actively rehabilitating stranded sea turtles for the last 15 years. Situated at the southern tip of Africa, the TCC is strategically located to receive post-hatchling loggerhead turtles. Over 1300 sea turtles have been successfully rehabilitated and released through the work of this program. Whilst sub-adult and adult turtles have been satellite tracked to confirm post-rehabilitation success, the small size of the post-hatchlings has prevented us from being able to track them, until now.

In a recent collaboration initiated by, Upwell Turtles, we have undertaken the first satellite tracking of young juvenile loggerhead turtles in South Africa. We tagged twelve rehabilitated juveniles (mean 621.32g, mean 14.24cm) with miniature Lotek satellite tags during January 2024, and another twelve turtles (mean 545.76g, mean 13.64cm) with the same tags during October 2024. The first group of turtles was released 22 nautical miles offshore southwest off the Cape Peninsula and the second group was transported to KwaZulu-Natal and released 1 nautical mile off Sodwana Bay, within the warmer waters of the Agulhas Current. The tracks have already revealed many fascinating insights about early-stage loggerhead dispersal and ecology. The data are also providing first-time evidence of medium-term post-release survivorship of early stage stranded turtles, demonstrating the efficacy and benefits of sea turtle rehabilitation efforts. This novel work is helping to better understand the movement of rehabilitated young loggerheads at sea and amplify the conservation message of these ocean ambassador.

Presented is a collaborative project between the four major public aquaria and registered sea turtle rehabilitation facilities in South Africa: PE Museum at Bayworld; East London Aquarium; SAAMBR (South African Association of Marine Biological Research); and Two Oceans Aquarium. For many decades these aquaria have been responsible for the rehabilitation and release of all five species of sea turtles commonly found in southern African waters. Said species include nesting Loggerheads (Caretta caretta) and Leatherbacks (Dermochelys coriacea); and transient Green (Chelonia mydas; Hawksbill (Eretmochelys imbricata) and Olive Ridley (Lepidochelys olivacea) turtles. Rehabilitation is costly and time consuming, and gauging the success of releasing rehabilitated individuals back into the wild is challenging. Globally, marine biotelemetry via the use of acoustic transmitters has been widely utilized. Acoustic transmitters can be externally attached to sea turtles from all species and life history stages, after which the animals’ movements are passively tracked via an array of moored inshore acoustic receivers. In recent years, acoustic telemetry has been widely utilized for the tracking of various fish and elasmobranch species along the South African coastline using the ATAP acoustic receiver array network. However, this has never been done for any sea turtle species. Historically in South Africa, most rehabilitated animals are sexually immature, too small for traditional satellite telemetry and therefore do not form part of the extensively monitored KZN Loggerhead and Leatherback nesting populations. By utilizing post-rehabilitation turtles as candidates for acoustic studies, rehabilitation facilities have ideal access and opportunity to study these subset populations. To date, 29 post-rehabilitation sea turtles from 3 of the 5 species (Greens, Loggerheads and Hawksbills) have been acoustically tagged and released, the majority of which are in the juvenile life history class. Novel movement patterns have been observed for a small number of individuals from each species tagged. The dataset from this ongoing study will form part of a long-term monitoring programme made possible by the longer battery life of acoustic transmitters. In addition to tracking movement patterns and post-rehabilitation success, comparisons of external acoustic transmitter attachment methods, including body attachment locations and adhesives used, will form part of this ongoing pilot study. Such a research project is essential in addressing the considerable knowledge gaps with regard to the movements of smaller sexually immature sea turtles off Southern Africa and provides a unique opportunity for improving acoustic tracking studies in the Western Indian Ocean region.